Medical device comprising a bio-compatible polymeric product with a layered structure

ABSTRACT

Disclosed is a method and a medical device comprising a bio-compatible polymeric product with a layered structure comprising at least one upper layer of a first polymeric component, a middle layer of a second polymeric component, and at least one lower layer of a third polymeric component, wherein the chain length of the first polymeric component and the third polymeric component is longer than the chain length of the second polymeric component. The medical device combines the features of strength, durability and bio-compatibility as well as it has resistance to tear and wear and has a good compressibility. A preferred design of the medical device is a cup produced from a care or film of LDPE surrounded by two layers of UHMWPE fabric. The medical device can be used as implants in mammals, especially as artificial cartilage within joints to secure mobility of the joint.

FIELD OF INVENTION

The present invention relates to polymers and products produced bypolymers. It discloses a method for enhancing the quality of polymerproducts, especially polymeric products that are to be exposed topressure, impact, wear and tear. The polymers disclosed herein areparticularly useful for cartilage substitution and for products to beutilised in medical devices. Especially the product can be used as anartificial joint spacer made to replace the missing cartilage, so thejoint can stay mobile. All patent and non-patent references cited in thepresent application, are hereby incorporated by reference in theirentirety.

BACKGROUND OF INVENTION

Many prosthetic medical devices are implanted into load-bearing jointssuch as knees, hips, etc. As such, these prosthetic devices must be verystrong and possess a high degree of wear resistance. Presently, theprosthetic medical device industry has utilised various metals andpolymers and combinations thereof to fabricate prosthetic devices.Unfortunately, both metals and polymers have drawbacks. For example,metals such as stainless steel, tungsten and titanium, and alloysthereof, may succumb to the corrosive environment of the body andeventually begin to wear. Such wear may result in fine metallicparticles being scraped away from the contact surface of the device andinto surrounding tissue and bone which may potentially cause pathogenicproblems. Polymers, such as polyethylene, polypropylene and nylons mayalso exhibit wear and may consequently produce particles which diffuseinto tissue and bone. Both metallic and polymeric particles shed fromthese prosthetic medical devices are of concern because they may beinherently reactive with the tissue and bone they contact, thus possiblycausing tissue degradation or necrosis.

Many medical devices are implanted into load-bearing joints such asknees, hips, etc, or utilised in the human body where mechanicalfunction provide high strength or shape stability such as heart valves,breast prosthesis, stent, catheter, etc. As such, these medical devicesmust be very strong and possess a high degree of wear resistance.Prosthetic medical devices manufacturers constantly work towarddeveloping better products by improving their physical properties.Improved wear resistance, for example, is a desirable quality to impartto a prosthetic medical device. Improving wear resistance without losingstrength or causing oxidative degradation is a difficult balance toobtain.

Generally, joint damage, such as cartilage damage, is treated byreplacing the joint with an artificial joint. However, seriouscomplications are caused by the replacement of artificial joints, inparticular a high occurrence rate of loosening problems resulting inbreakage of the bones around the artificial joint. In the case ofcartilage damage a repair with cartilage substitution placed into intactbones is to be preferred instead of replacing the entire joint.

Various methods have been devised attempting to reduce the wear rate ofthe load bearing prosthetic medical devices. For polymers, a commonpractice within the prosthetic medical device industry is to usecross-linked polymers and resins to form the medical device. Polymersare commonly cross-linked by chemical catalysis or irradiation exposure.Most cross-linking methodologies do result in greater wear resistance.However, indiscriminate or uncontrolled cross-linking may result in theformation of a weakened polymeric matrix, not capable of withstandingthe enormous pressures placed on the devices in the patient resulting indegradative wear as described above.

One common practice within the medical device industry is to usecross-linked polymers and resins to form the medical device.“Cross-linked” polymers are defined as polymeric materials which havebeen subjected to chemical or radiation-initiated activation resultingin dendritic bond formation between and amongst individual polymericchains yielding new intermolecular and intramolecular networks. Thesecross-linked networks within the polymer provide chemical and physicalproperties, which are usually different from the virgin polymer. Suchproperties include increased wear and creep resistance, durability, etc.Indiscriminate or uncontrolled cross-linking of the polymeric materialcomprising the medical device may result in improved wear resistance,but strength and other desirable properties may be sacrificed.

Ultrahigh molecular weight polyethylene (hereinafter referred to as‘UHMW poly-ethylene’ or ‘UHMWPE’) is commonly used to make prostheticjoints such as artificial hip joints. In recent years, it has becomeincreasingly apparent that tissue necrosis and interface osteolysis, inresponse to UHMW polyethylene wear debris, are one cause of thelong-term loosening failure of prosthetic joints. For example, theprocess of wear of acetabular cups of UHMW polyethylene in artificialhip joints introduces many microscopic wear particles into thesurrounding tissues. The reaction of the body to these particlesincludes inflammation and deterioration of the tissues, particularly thebone to which the prosthesis is anchored. Eventually, the prosthesisbecomes painfully loose and must be revised. It is generally accepted byorthopaedic surgeons and biomaterials scientists that the reaction oftissue to wear debris is the chief cause of long-term failure of suchprostheses.

U.S. application 20020007219 describes radiation and melt treated ultrahigh molecular weight polyethylene prosthetic devices. The referencedescribes a medical prosthesis for use within the body which is formedof radiation treated ultra high molecular weight polyethylene havingsubstantially no detectable free radicals. Preferred prostheses exhibitreduced production of particles from the prosthesis during wear of theprosthesis, and are substantially oxidation resistant. Methods ofmanufacture of such devices and material used therein are alsodescribed.

U.S. application 20020037944 describes crosslinking of polyethylene forlow wear using radiation and thermal treatments. Described are methodsfor enhancing the wear-resistance of polymers, the resulting polymers,and in vivo implants made from such polymers. One embodiment of theinvention presents a method whereby a polymer is irradiated, preferablywith gamma radiation, then thermally treated, such as by remelting orannealing. The resulting polymeric composition preferably has its mostoxidized surface layer removed. Another embodiment of the inventionpresents a general method for optimizing the wear resistance anddesirable physical and/or chemical properties of a polymer bycross-linking and thermally treating it. The resulting polymericcomposition is wear-resistant and may be fabricated into an in vivoimplant.

U.S. application 20010049401 describes chemically crosslinked ultrahighmolecular weight polyethylene for artificial human joints. Disclosed isa method for enhancing the wear-resistance of polymers by crosslinkingthem, especially before irradiation sterilization. In particular, theinvention presents the use of chemically crosslinked ultrahigh molecularweight polyethylene in in vivo implants.

SUMMARY OF INVENTION

A first aspect of the present invention relates to a medical devicecomprising a biocompatible polymeric product with a layered structurecomprising at least one upper layer of a first polymeric component, amiddle layer of a second polymeric component, and at least one lowerlayer of a third polymeric component, wherein the chain length of thefirst polymeric component and the third polymeric component are longerthan the chain length of the second polymeric component.

The first and third polymeric component may be similar or the first andthird polymeric component may be different from each other.

In a preferred embodiment the present invention provides methods ofproducing medical devices. In another preferred embodiment the presentinvention provides methods of producing polyethylene medical devices.Specifically, the invention provides a stratified polymeric structure toproduce the medical devices having improved wear characteristics. Atleast three layers of polymers are stratified, and said stratifiedproduct may be pressed into shape.

By the term ‘medical device’ is to be understood any device which can beused shortly or more permanently in any process including a medicaltreatment of an individual.

The term ‘stratified’ is used synonymously with the terms ‘layered’ and‘stacked’ and means that the product is made by three or more layers orstrata of polymer material.

The characteristics of the medical product in the present invention ishigh tensile strength and improved wear resistance as well as capabilityof absorbing shocks, impacts and pressure load, due to the stratifiedstructure of the device and cross-linked polymers within the device.Wear resistance can also mean wearability.

The term ‘layered structure’ especially describe features according tothe method of formation of the polymer product of the devices, althougha layered structure may be or may not be visible macroscopically orobservable microscopically within the device produced by the polymericcomponents. The layered structure of a device may be realised bychemical analysis of the polymeric product and also by microscopicmethod comprising light microscopy, contrast microscopy or NMRmicroscopy. A surface layer of the medical device is optional. Thesurface layer of the device can only be detected by chemical analysis.

In a preferred embodiment a cartilage substitute is produced comprisingthe polymeric material, said cartilage substitute may substitute fordamaged cartilage especially within joints with intact bones, where itis being capable of partly or completely fill the role of naturalcartilage in the joint.

The present invention also provides for the fabrication of various typesof prosthetic devices and other medical devices. While the invention isnot limited to any particularly shaped medical and prosthetic device,the preferred shapes include acetabular cups, hip endo-prostheses,knees, ankles, shoulders, tibial and femoral joints, finger and thumbmembers, vertebra, elbows, foot and toe members and wrist members aswell as breast prosthesis, heart valves, stents, and catheters.

In one embodiment of the invention, the polymeric materials produced inrelatively thin layers are stacked, preferred is a combination wherelayers with different constitution are located against each other.Layers comprising polymeric materials of two or more constitutions areutilised. Preferably one layer is composed of one polymeric material.One polymeric material comprises long polymeric chains such as fibres,whereas the other polymeric material comprises short chain polymermaterial. The thickness of each polymer layer of the device is selectedin accordance to the thickness of the device and the number of layersdecided to utilise for the device, a preferred thickness of each polymerlayer is between 0.1 mm and 10 mm, optional but also preferred is adevice constructed of polymer layers wherein the long polymer fibre arecomprised in thinner polymer layers than the layers of the short chainpolymer material.

Medical devices manufactured from the stratified polymer layers of theinvention may be moulded in one or more processes comprising heating,vacuuming and pressing. The stacked polymer layers are conducted to heatto combine the polymer layers, simultaneously or afterwards the polymerproduct is conducted to a press in vacuum where the overall shape of themedical device is controlled. Any surplus of polymer material may be cutaway.

The medical devices can be produced with attachments, or one or moreapertures to improve the functionality within the body of the individualreceiving the medical devise or to fasten the device in said body.

Accordingly, another aspect of the invention is a method for producing amedical device of a polymeric product, said method comprising obtaininga number of at least three polymer layers, and positioning the polymerlayers in a sandwich composition, and shaping the sandwich compositionof polymer layers by heating said composition followed by pressing itinto a mould, where the heating and pressing processes are conducted invacuum, and providing the polymeric product in a desired shape.

In an embodiment the medical device is subjected to irradiation tocross-link the polymeric material, the radiation source can be, but isnot limited to, high-energy electrons, gamma rays, light photons,microwaves, preferred is high-energy electrons and gamma rays, morepreferred is high-energy electrons.

To reduce the friction between the medical polymeric device and itssurroundings in the body, the shaped polymeric product may be subjectedto surface coating, the surface coating may be any bio-compatiblecoating material capable of reducing friction. In a preferred embodimentthe product is coated with 10-500 nanometer of polyvinylpyrrolidone(PVP) by a plasma polymerisation treatment. The surface coatingincreases the lifetime of the device by increasing lubricatingproperties ant thereby decrease the friction.

Definitions

LDPE=Low-density polyethylene

UHMWPE=Ultra high molecular weight polyethylene

The term ‘core’ is used to describe a layer of polymer; said layer ismade of short chain polymer material. The short chain polymer materialof the core is cast to the desired thickness. The core is primarily usedto enhance the capability of the device to absorb shocks, impacts andpressure load, the core can also attach two layers of fabric to eachother.

The term ‘fabric’ is used to describe a layer of polymer; said layer ismade of long polymer chains, such as polymer fibre. The fibres arecombined in a textile structure.

The term ‘fibre’ is used as a unit of molecules, where the fibre is ofrelatively short length, and further characterised by a high ratio oflength to thickness or diameter.

The term ‘filament’ is used as a single textile element of smalldiameter and very long length considered as continuous.

The term ‘film’ is used to describe a layer of polymer; said layer ismade of short chain polymer material. The short chain polymer materialof the film is cast to the desired thickness. The film is primarily usedto attach two layers of fabric to each other, but also provide importantfeatures to the device as described below.

The term ‘inlay’ is used to describe a smaller layer of polymer; saidlayer is made of short chain polymer material. The short chain polymermaterial of the inlay is cast to the desired shape and thickness. Theinlay is primarily used to enhance the capability of the device toabsorb shocks, impacts and pressure load in areas of the devicesubjected to higher degrees of pressure and shocks.

The term ‘implant’ is used for a device, which is inserted into the bodyin order to replace or substitute for a function, which has been lost orimpaired.

By the term ‘medical device’ is to be understood any device which can beused shortly or more permanent in any process including a medicaltreatment of an individual. In particular the ‘medical device’ may be animplant, wherein the term implant refers to a device meant to beinginserted into the human or animal body for a long period of time, forexample several years. The term ‘strand’ is used as an assembly ofparallel filaments simultaneously produced and lightly bonded.

DESCRIPTION OF DRAWINGS

FIG. 1 illustrates one three-layered stratified structure of the medicaldevices comprising fabric-core or inlay-fabric.

FIG. 2 illustrates the three-layered stratified structure of FIG. 1which is surface coated.

FIG. 3 illustrates one three-layered stratified structure of the medicaldevices comprising fabric-film-fabric.

FIG. 4 illustrates the three-layered stratified structure of FIG. 3which is surface coated.

FIG. 5 illustrates one five-layered stratified structure of the medicaldevices comprising fabric-core or inlay-fabric-film-fabric.

FIG. 6 illustrates the five-layered stratified structure of FIG. 5 whichis surface coated.

FIG. 7 illustrates one surface coated seven-layered stratified structureof the medical devices comprising fabric-film-fabric-core orinlay-fabric-film-fabric.

FIG. 8A illustrates the seven-layered stratified structure of FIG. 7 aswell as a cup-shaped device produced from said layered structure (8B)and sealing of the rim (8C).

FIG. 9 illustrates a flow chart in the production of the device.

FIG. 10 illustrates a human hip joint in which one embodiment of amedical device according to the invention is located in situ.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a desirable balance of improved wearresistance and high tensile strength and toughness in the polymericcompositions used for medical devices. It has been discovered that wearresistance can be improved without sacrificing other desirableproperties such as toughness or strength by controlling the amount ofdifferent polymeric substrate comprising the prosthetic device.Referring to FIG. 1, the stratified structure of the medical devices isillustrated. The products of the invention has a high tensile strengthand improved wear resistance as well as the capability to absorb shocks,impacts and pressure load, also it reduces the amount of tearing off.

The material for the medical devices is primary polymers, with at leastone layer of a first polymeric component with high molecular weight, andat least a layer of a second polymeric component with low molecularweight. This combination of longer and shorter polymers provides thefeature of the device comprising strength as measured by tear, tensionand compression.

The main aspect of the invention is a medical device comprising abio-compatible polymeric product with a layered structure comprising atleast one upper layer of a first polymeric component, a middle layer ofa second polymeric component, and at least one lower layer of a thirdpolymeric component, wherein the chain length of the first polymericcomponent and the third polymeric component is longer than the chainlength of the second polymeric component.

The essence of the present invention is the selection of the compositionof the different polymer layers as well as the selection of the numberof polymer layers comprising first, second and third polymericcomponents, as well as thickness of said polymer layers and also sizeand position of an optional layer of the second polymeric component.

Another embodiment of the present invention provides for layers ofpolyolefinic polymers and resins. Within the context of the presentinvention, a polymer is defined as an organic compound having repeatingunits of similar or different monomers. A resin is defined herein as apartially cured polymer having utility as a mouldable material suitablefor curing into a solid article.

In an embodiment the polymers and resins of the polymer layers of thepresent invention may be polyolefinic polymers, polyethylene,polypropylene, polyacrylates, polystyrene, polytetrafluorethylene,polyvinylalcohol, polyethylene oxides, polyvinylpyrrolidon, polysilanes,polyurethanes, polyethers, polyamides, polyesters, polyalkyl acrylates,nylon, rubber and epoxy resins. It should be understood that the abovelist of polymers is not exhaustive, and other polymers may also beemployed in the present invention. Preferred is polyethylene andpolypropylene. Most preferred is polyethylene.

Preferably, the polymer materials of the first, second and/or thirdpolymer layer may be from the group of polyethylenes or the group ofpolypropylenes such as polyethylene (PE), polypropylene (PP), highmolecular weight polypropylene (HMWPP), high molecular weightpolyethylene (HMWPE), ultra high molecular weight polyethylene (UHMWPE)and ultra high molecular weight polypropylene (UHMWPP), high densitypolyethylene (HDPE), low density polyethylene (LDPE), high densitypolypropylene (HDPP) and low density polypropylene (LDPP), ultra highdensity polyethylene (UHDPE), ultra high density polypropylene (UHDPP),cross-linked polyethylene, non-cross-linked polyethylene, cross-linkedpolypropylene, and non-cross-linked polypropylene. In this embodiment ofthe present invention, any combination of polymers listed above, ortheir equivalents, may be used.

First Polymeric and Third Polymeric Component

The polymers comprising the first polymeric component- and the thirdpolymeric component are preferable above 100 monomer units, such asabove 1,000 monomers units, for example above 10,000 monomer units,preferable above 20,000 monomer units, more preferable above 30,000monomer units, further preferable above 40,000 monomer units, yetfurther preferable above 50,000 monomer units, most preferable above60,000 monomer units.

The polymers of the upper and lower layer comprising first and thirdpolymeric components of the present invention have preferably molecularweights ranging between 1,000 and 100,000,000 such as between 10,000 and75,000,000, for example between 50,000 and 50,000,000, preferablebetween 75,000 and 25,000,000, more preferable between 100,000 and1,000,000, further preferable between 200,000 and 800,000, yet furtherpreferable between 300,000 and 700,000 most preferable between 400,000and 600,000

In a preferred embodiment the polymers comprising the first polymericcomponent and the third polymeric component are comprises long polymerfibres, filaments or strands produced from the polymers presented above,preferred polymers to produce said fibre and filaments may be selectedfrom the group of poly-ethylenes including, but not limited to, highmolecular weight polyethylene (HMWPE), ultra high molecular weightpolyethylene (UHMWPE), high density polyethylene (HDPE), ultra highdensity polyethylene (UHDPE), cross-linked polyethylene andnon-cross-linked polyethylene. The most preferred polymer of theinvention is fibre produced from UHMWPE. The polymers of the firstpolymeric component and the third polymeric product provide strength andwear resistance to the device.

A preferred polymer of the upper and lower layer of the invention isUHMWPE, and a preferred combination is UHMWPE and HDPE.

Additional components of the upper and lower layer polymeric materialmay be incorporated into the matrix in a braided, woven, spongy orspiral pattern, the fibres and filaments comprising the additionalcomponents having reinforcing properties. The fibres may be inorganicfibres such as carbide, nitride, boride, carbon and oxide fibres, or thereinforcement may be of organic origin such as Dacron.

The Second Polymeric Component

The middle layer comprising a second polymeric component can beconstructed from short chain polymer material; the polymers may beselected from the polymers presented above. Short chain polymers mayhave less than about 100 units, such as less than about 90 units, forexample less than about 80 units, preferable less than about 70 units,more preferable less than about 60 units, further preferable less thanabout 50 units, yet further preferable less than about 40 units, mostpreferable less than about 30 units. The short chain polymer materialmay not have cross links and only weak Van der Waals forces betweenchains, The molecular weight is preferably less than about 10,000, suchas less than about 9,000, for example less than about 8,000, preferableless than about 7,000, more preferable less than about 6,000, furtherpreferable less than about 5,000, yet further preferable less than about4,000, most preferable less than about 3,000.

Preferred polymers to produce the middle layer constituting film, coreand inlay polymer layers may be selected from the group ofpoly-ethylenes or from the group of polypropylenes including, but notlimited to polyethylene (PE), polypropylene (PP), high molecular weightpolyethylene (HMWPE), high molecular weight polypropylene (HMWPP), highdensity polyethylene (HDPE), high density polypropylene (HDPP), lowdensity polyethylene (LDPE) and low density polypropylene (LDPP).Preferred is short chain polymer material such as LDPE and LDPP. Furtherpreferred are polymers which are branched. Most preferred is short chainpolymer material of polyethylene.

From the above mentioned first, second and third polymeric componentsdifferent polymer layers comprising fabric, film, core and inlay areconstructed. These polymer layers are further described below.

Fabric

From the longer polymers comprising the first and/or the third polymericcomponent as previously described a fabric may be constructedconstituting the upper and lower layers of a medical device. Preferredis a fabric of UHMWPE fibre. The fabric corresponds to the first and/orthird polymeric component as described elsewhere herein.

Within the fabric, the first polymeric component and the third polymericcomponent are preferably in the form of fibre. Methods of constructionof fibres are known to persons skilled in the art. The polymers may bealigned and/or spun into fibre by gel spinning or filaments, which againmay be spun into strands. From said fibres and/or filaments and/orstrands the layers of polymeric materials may be manufactured.

The fabric may be produced into a suitable shape, said shape ispreferably constructed by weave, knit, crochet, stitch, plait,interlace, intertwine, interlock, link or unite the fibre and/orfilaments and/or strands in other ways such as non-woven techniques.Preferable the fabric is woven or knitted.

In an embodiment the fabric can be woven using different techniques,said techniques include but is not limited to cord woven, linen woven,mat woven, Celtic woven and twill woven. Persons skilled in the art knowvariations of these techniques, said variations is hereby incorporated.

According to an embodiment of the invention the polymer fibres are woveninto a squared fabric comprising intercepts with angles of 90 degree.The dimension and weaving style of the fabric is optional, preferred isa binding style of 3:1 (twill). The fabric can if the thickness allowsit be rolled into a roll, from which suitable pieces are detached beforethe stratified polymer product is constructed. Products which can beused comprises but is not limited to fabric of Dyneema® from DSM,Spectra® from Allied Signal Inc. Preferably the fabric is workable inthe process of construction of the medical device as described elsewhereherein.

In another preferred embodiment the fibres, filaments or strands of theconstitution described above are woven into the fabric in a shapesuitable for the shape of the polymeric product. The shape of the fabriccan be any possible shape including but not limited to round, oval,triangle, quadrangle, square, rectangular, pentagon, hexagonal etc. andmay be symmetrical or asymmetrical in any direction. Preferred shapes ofthe fabric are quadrangle and round.

In one embodiment the fibres in each layer of the fabric are positionedover each other making a structure wherein the angles of the intersectare of 1 to 179 degree, such as in angles of 40 to 150 degree, forexample such as in angles of 60 to 130 degree, such as in angles of 70to 10 degree, for example such as in angles of 80 to 100 degree, such asin angles of about 90 degree. Most preferred is intersects of fibre andstrands in angles of about 90 degree.

The thickness of the fabric is preferably determined by thickness aswell as the number of fibres and/or filaments and/or strands and thedistance between these fibres, filaments and strands in the fabric. Theoverall thickness of the fabric is preferably between 0.001 mm and 3 mm,preferred is between 0.01 mm and 2 mm, more preferred is between 0.02 mmand 1.5 mm, further preferred is between 0.03 mm and 1.0 mm, yet furtherpreferred is between 0.04 mm and 0.08 mm, most preferred is between 0.05mm and 0.06 mm.

In an embodiment the area weight of the fabric is preferred betweenabout 10 g/M² and 500 g/M² preferred is an area weight of between about50 g/M² and 300 g/M², more preferred is an area weight of between about75 g/M² and 250 g/M², further preferred is an area weight of betweenabout 100 g/M² and 200 g/M², yet more preferred is an area weight ofbetween about 125 g/M² and 175 g/M², even more preferred is an areaweight of between about 140 g/M² and 160 g/M², most preferred is an areaweight of about 150 g/M².

The fibres, filaments and strands from which the fabric is producedaccording to the description herein, may have a fibre diameterpreferably between 100 and 650 dtex. The fibre diameter of the warpyarnis preferably about 300-650 dtex, more preferably about 350-550 dtex,further preferably about 400-500 dtex, most preferably about 430-460dtex. The weftyarn is preferably about 100-350 dtex, more preferablyabout 150-300 dtex, further preferably about 175-250 dtex, mostpreferably about 210-230 dtex.

The fabric need not be constructed of fibre or filaments or strands withequal thickness. A woven fabric where some of the strands have a largerthickness than the rest may be used. In this way e.g. every second,every third or more strands in between may have a larger thickness thanthe rest of the strands of the fabric.

The fabric described herein may also be constructed by strands ofdifferent polymers. Said different polymers may be selected among thepolymers listed herein above. Two or more polymers maybe used in theconstruction of the fabric.

In an embodiment the thickness of the fabric may vary according todifferent thickness of the polymer strands as described above ordifferent polymers utilised to construct the fabric. Also differentnumbers of strands pr cm may be used.

In an embodiment the surface dimension of one or more inner layers offabric may be smaller than the total surface dimension of a medicaldevice. Smaller layers of fabric may enclose inlays.

In another preferred embodiment the fabric has a high tensile strengthand a high wear resistance. The degree of tensile strength is determinedby the polymer utilised to produce the fibre and the thickness of thefibre. The tensile strength of the strand or fibre in a fabric ispreferably above 1.0 GPa, such as above 1.2 GPa, preferable above 1.4GPa, more preferable above 1.6 GPa, further preferable above 1.8 GPa,yet further preferable above 1.9 GPa, most preferable above 2.0 GPa.

In another embodiment the tensile strength of the strand or fibre in afabric is preferably above 0.05 GPa, such as above 0.1 GPa, preferableabove 0.3 GPa, more preferable above 0.5 GPa, further preferable above0.7 GPa, yet further preferable above 0.8 GPa, most preferable above 0.9GPa.

Although the term ‘fibre’ is used in the description of fabriccomprising the first and third polymeric components, filaments and/orstrands and/or other components comprising long chains of polymer unitsmay be used instead of fibres.

The fabric constitute a reinforcement fabric or tissue of the device.

Film, Core and Inlay

The middle layer of the polymeric product comprises a second polymericcomponent. Said polymeric component may be any short chain polymermaterial or low density polymer material as described above. Alsochopped strands of long chain polymer material such as fibre and/orfilaments and/or strands may be utilised as short chain polymermaterials. Preferred is when the chopped strands comprising short chainpolymers are moulded into a matrix with low density polymer material ora polymer comprising the second polymeric component as describedelsewhere herein.

By ‘chopped strands’ is meant shorter chains or strands cut from fibresand/or filaments and/or strands.

In an embodiment said middle layer comprising polymer layer comprises afilm, a core or an inlay.

The polymer layers ‘film’, ‘core’ and ‘inlay’ may be produced of similaror substantially similar or different polymers. Preferred are polymerlayers of film, core and inlay which are produced by similar polymers.Polymers suitable to be used are described above.

The differences of film, core and inlay may be the dimensions of thepolymer layers. Said dimensions are determined according to the functionof the polymer layers. The film, core and inlay may differ in thicknessfrom each other, but may also have similar thickness, whereby film andcore sometimes can substitute each other in the composition of themedical device.

The visual difference of film and core is preferably based on thethickness, where the film in general is thinner than the core. The mainpurpose of a film layer is to attach two layers of fabric to each other,and simultaneously provide the device with characteristics such ascapability of absorbing shocks, impacts and pressure load.

The core may also attach fabrics to each other, and provide the samecharacteristics to the device as the film, but the core may be utilisedin devises subjected to higher degree of impacts and pressure load thanto devises comprising no core layer.

The difference of core and inlay may be based on the length and width ofthe polymer layers, the inlay may be smaller than a core. The functionof an inlay is to absorb shocks and pressure in specific areas of amedical device. An inlay of one device may be larger than a core ofanother device.

In an embodiment said middle layer comprises a film or core or inlay.The film and core comprises the polymers described above, and may beconstructed by melting said polymers. Mixtures of polymers may be usedto construct the film, core or inlay. The melted polymeric mass may beformed according to any method possible, said methods are known topersons skilled in the art. Said methods comprises but are not limitedto blow moulding, extruding, foil moulding, injection moulding,compression moulding, preferred is blow moulding. Preferred methods aremoulding of the melted polymeric mass in small or large open moulds/vatsor injection moulding, the thickness of the material is optional, but ischosen not to be changed followed solidification. Followingsolidification the solidified polymeric matrix can be cut or punched orstamped out to a suitable dimension.

The suitable dimension of the film may be determined in accordance tothe scope of the application. The preferred application of the film isas a thin polymer layer between two layers of fabric, in this situationthe size comprising length and width of the film is at least the lengthand width of the polymeric material used to produce a medical device,hereby the film may be squared, circular or any other dimension as anysurplus of polymer material is removed following formation of themedical device.

In an embodiment the device is constructed from layers of fabric, film,core and/or inlay where said layers each has a dimension suitable toconstruct the device without any process of removing surplus of polymerlayers. In this process the polymer layers of film, core and/or inlaymay have dimensions smaller than the outermost layer of fabric. Toadjust the size of the polymer layers to the form of the device to beproduced, inner layers of fabric may be smaller than the outermost layerof fabric. The outermost layer of fabric which constitute the inner sideof a medical device may also be smaller than the outermost layer offabric which constitute the outer side of a medical device.

The suitable dimension of the core may also be determined in accordanceto the scope of the application. The preferred application of the coreis as a polymer layer between two layers of fabric, where the core fillsin all the area comprising length and width between said two layers offabric, in this situation the size of the core is at least the lengthand width of the polymeric material used to produce a medical device,hereby the core may be squared, circular or any other dimension as thesurplus of polymer material is preferably removed following formation ofthe medical device.

The suitable dimension of the inlay may also be determined in accordanceto the scope of the application. The preferred application of the inlayis as a polymer layer, which fills in part of the area between twolayers of fabric or film; hereby the inlay may comprises any dimensionappropriate for the purpose of the medical device. The inlay is mouldedinto the appropriate dimension or it is cut into the appropriatedimension.

The preferred thickness of the core and of the inlay is chosen inaccordance with a reduction of said thickness in the construction of thedevice. During the pressing process the thickness of the core and theinlay may be reduced by up to 50%, as the short chain polymers of theinlay and/or of the core are pressed in between layers of fabric. Bythis pressing process the other dimensions comprising length in twodimensions of the core and inlay may increase as the thicknessdecreases.

Objects of non-polymeric material or objects of polymeric materialdifferent to the material which the core or inlay is made of, may beplaced within core or inlay. Said objects may be but is not limited tometal globes or metal sheets. The objects may be incorporated in theinlay or core in the moulding process or may be placed in holes made inthe inlay or core in the moulding process or made afterwards. Anexamples of objects in an inlay is metal globes in the inlay.

The difference of film and core has a fluid borderline, whereby theutility of film and core may be interchangeable. Also the difference ofcore and inlay has a fluid borderline, whereby the utility of core andinlay may be interchangeable

In an embodiment the film is prepared as described elsewhere, the filmis preferably between 0.001 and 5 mm thick, such as between 0.01 and 5mm, preferable between 0.1 and 4 mm, more preferable between 0.2 and 3mm, further preferable between 0.3 and 2 mm, yet further preferablebetween 0.4 and 1.5 mm, most preferable between 0.5 and 1 mm.

The core or inlay which are also prepared as described elsewhere, ispreferably between 0.1 and 30 mm thick, such as between 0.2 and 25 mm,preferable between 0.3 and 21 mm, more preferable between 0.4 and 17 mm,further preferable between 0.5 and 13 mm, yet further preferable between0.6 and 10 mm, most preferable between 0.7 and 7 mm.

In an embodiment the surface dimension of one or more layers of film maybe smaller than the total surface dimension of a medical device. Smallerlayers of film may be used on one or more sides of smaller size fabric.

In a preferred embodiment the polymers as described above are of medicalgrade.

The film, core and inlay comprises short chain polymers. Examples ofcharacteristics, properties and additives of said short chain polymersare shown in the following tables Method Unit Value Characteristics Meltindex ISO 1133 G/10 min 0.8 Density ISO 1183 G/cm³ 0.924 Property YieldStress ISO R527 Mpa 12 Tensile Strenght at break ISO R527 Mpa 14Elongation at break ISO R527 % 650 Modulus of elasticity ISO 527-2 Mpa240 Melting point ISO 11357-3 ° C. 114 Vicat temperature ISO 306 ° C. 98

Mechanical properties measured on a moulded plaque.

More preferred examples of characteristics, properties and additives ofsaid short chain polymers are shown in the following tables Method UnitValue Characteristics Melt index ISO 1133 G/10 min 2.18 Density ISO 1183G/cm³ 0.922 Property Yield Stress ISO R527 Mpa 11 Tensile Strenght atbreak ISO R527 Mpa 10 Elongation at break ISO R527 % 550 Modulus ofelasticity ISO 5527 Mpa 210 Melting point ISO 11357-3 ° C. 112 Meltingpoint ISO 11357-3 ° C. 94 Shore hardness ISO 868 52

Mechanical properties measured on a moulded plaque.

Processing at an advised temperature of 150° C. to 180° C.

Additives may be used in the short chain polymer material, preferred isnone slip agent and none anti-blocking additives.

An example of a short chain polymer material is Lacqtene® FE 8000 fromAtofina.

Production of the Layered Polymeric Product

In one embodiment the polymeric product from which medical devices areconstructed comprises polymer layers in a sandwich or laminated formatwith at least three polymer layers, where the polymer layers are fusedtogether by a heating process. The middle or at least one inner layerdiffers from the two or more outer layers, hereby the polymer layersconstitute a film, or a core or an inlay with at least one layer offabric on each side. The fabric provides a high wear resistance and hightensile strength, while the inlay and core and to some degree also thefilm absorbs shocks.

In the production of a medical device, the different polymer layers asdescribed above are laminated in accordance to the requiredcharacteristics of said medical device. In an embodiment the middle orat least one inner layer of the polymeric product constitute a core or afilm, on each side of the core or film a fabric is positioned. In apreferred embodiment the polymeric product are composed of three layerswhere the fabrics at the different sides of the core have equalconstitutions.

The layers of fabrics within a device can be different according to thepolymers utilised to produce the fabrics or the fibres or strands withinthe fabrics may be different, or the fabrics are produced in differentways, also the fabrics can have different thickness. In a cup shapeddevice the outer part of the cup may comprise a thicker fabric than theinner part of the cup, hereby increasing the wear resistance of theouter part.

In another embodiment the polymeric product are composed of more thanthree layers, where, in between two fabrics a film or a core or an inlayare positioned. The individual layers of fabric may be substantiallyidentical, identical or different in composition. Also the layers offilm, core and inlay may be substantially identical, identical ordifferent in composition.

In an embodiment the number of the layers core, film, inlay and fabricsdiffer across the polymeric product. The number of the layers can alsovary in different areas of the polymeric product. The outermost layer ofeach side of the product must be fabric, and two layers of fabrics havea film or a core or an inlay in between. With varying number of layersacross the polymeric product, also the thickness of the product varies.Some areas may contain an inlay other areas may be without said inlay.

In a further embodiment the outermost layer of the product can be afilm. Said film is positioned next to a layer of fabric. Both sides of aproduct may have film layers as the outermost layers or only one side isa film layer. In case the medical device has more than two outer sides,one or more sides may be a film layer.

The polymeric product can also constitute two or more layers of fabricson each side of a core or an inlay, and said two or more layers offabrics may have a film of a polymer layer in between each fabric.Following heating of the layered polymeric product the film and/or coreand/or inlay mechanically connect or bond together two layers of fabric.

Layers of film and/or core and/or inlay in a device may be differentaccording to the polymer utilised to produce said layers. The polymersmay be of different types, preferred polymers are mentioned hereinabove. Also the polymers may be mixtures of different types of polymersor mixtures of polymer chains of different length or both.

Film may have a higher adhesiveness than core and inlay.

The number of layers of fabric in a medical device is optional, as wellas the number of layers of film and fabric and inlay can differ on eachside of a core or of an inlay. The number of layers of fabric in amedical device is preferably between 1 and 100, such as between 2 and50, for example between 2 and 40, preferable between 2 and 35, morepreferable between 2 and 30, further preferable between 2 and 25, yetfurther preferable between 2 and 20, most preferable between 2 and 10.

Also the number of layers of film in a medical device is optional, thenumber of layers of film is preferably between 0 and 100, such asbetween 1 and 50, for example between 1 and 40, preferable between 1 and35, more preferable between 1 and 30, further preferable between 1 and25, yet further preferable between 1 and 20, most preferable between 1and 10.

In addition the number of layers of core in a medical device isoptional, the number of layers of core is preferably between 0 and 100,such as between 1 and 50, for example between 1 and 40, preferablebetween 1 and 35, more preferable between 1 and 30, further preferablebetween 1 and 25, yet further preferable between 1 and 20, mostpreferable between 1 and 10. The number of layers of film, inlay andfabric can be different at each side of a core.

The number of layers of inlays in a medical device is optional, thenumber of layers of inlay is preferably between 0 and 100, such asbetween 1 and 50, for example between 1 and 40, preferable between 1 and35, more preferable between 1 and 30, further preferable between 1 and25, yet further preferable between 1 and 20, most preferable between 1and 10. The inlay can be positioned anywhere within the stratifiedpolymer product between two layers of film or fabric. The inlay may besmaller than the entire area of the medical device, and the inlay may belocated at any position within the medical device. Also the number oflayers of film, core and fabric can be different at each side of aninlay.

Preferred layered compositions of the polymeric product of medicaldevices comprises but are not limited to the constitutions:

-   -   fabric-film-fabric.    -   fabric-core-fabric.    -   fabric-film-core-film-fabric    -   fabric-film-fabric-core-fabric-film-fabric.    -   fabric-film-fabric-film-fabric-core-fabric-film-fabric-film-fabric.    -   fabric-film-fabric-film-fabric-film-fabric-core-fabric-film-fabric-film-fabric-film-fabric.    -   fabric-film-fabric-film-fabric-film-fabric-film-fabric-core-fabric-film-fabric-film-fabric-film-fabric-film-fabric.    -   fabric-core-fabric-film-fabric-film-fabric.    -   fabric-film-fabric-core-fabric-film-fabric-core-fabric-film-fabric.    -   fabric-film-fabric-film-fabric-film-fabric-core-fabric-film-fabric.    -   fabric-film-inlay-film-fabric.    -   fabric-film-fabric-film-inlay-film-fabric-film-fabric.    -   fabric-film-inlay-film-fabric-film-fabric-film-fabric.    -   fabric-film-inlay-film-fabric-film-inlay-film-fabric.    -   fabric-film-inlay-film-fabric-film-fabric-film-inlay-film-fabric.    -   fabric-film-inlay-film-fabric-film-inlay-film-fabric-film-fabric.    -   fabric-film-inlay-film-fabric-film-inlay-film-fabric-film-inlay-film-fabric.    -   fabric-film-inlay-film-fabric-film-fabric-film-inlay-film-fabric-film-inlay-film-fabric.    -   fabric-film-inlay-film-fabric-film-fabric-film-fabric-film-inlay-film-fabric-film-inlay-film-fabric.    -   fabric-film-inlay-film-fabric-film-inlay-film-fabric-film-inlay-film-fabric-film-fabric.    -   fabric-film-fabric-inlay-fabric-film-fabric.    -   fabric-film-fabric-film-fabric-inlay-fabric-film-fabric-film-fabric.    -   fabric-film-fabric-inlay-fabric-film-fabric-film-fabric-film-fabric.    -   fabric-film-fabric-inlay-fabric-film-fabric-film-fabric-inlay-fabric-film-fabric.    -   fabric-film-fabric-inlay-fabric-film-fabric-film-fabric-film-fabric-inlay-fabric-film-fabric.    -   fabric-film-fabric-inlay-fabric-film-fabric-film-fabric-inlay-fabric-film-fabric-film-fabric.    -   fabric-film-fabric-inlay-fabric-film-fabric-film-fabric-inlay-fabric-film-fabric-film-fabric-inlay-fabric-film-fabric.    -   fabric-film-fabric-inlay-fabric-film-fabric-film-fabric-film-fabric-inlay-fabric-film-fabric-film-fabric-inlay-fabric-film-fabric.    -   fabric-film-fabric-inlay-fabric-film-fabric-film-fabric-film-fabric-film-fabric-inlay-fabric-film-fabric-film-fabric-inlay-fabric-film-fabric.    -   fabric-film-fabric-inlay-fabric-film-fabric-film-fabric-inlay-fabric-film-fabric-film-fabric-inlay-fabric-film-fabric-film-fabric.    -   film-fabric-film-fabric-film.    -   film-fabric-core-fabric-film.    -   film-fabric-film-core-film-fabric-film.    -   film-fabric-film-inlay-film-fabric-film.    -   fabric-film-fabric-film.    -   fabric-core-fabric-film.    -   fabric-film-core-film-fabric-film.    -   fabric-film-inlay-film-fabric-film.    -   fabric-film-fabric-inlay-fabric-film-fabric-film.

Wherein fabric comprises the first and/or third polymeric component asdescribed elsewhere herein, and film, inlay and core comprise the secondpolymeric component as described elsewhere herein.

The layers of fabrics within a device may be similar or may be differentin the construction. Also one or more layers of fabrics within a devicemay differ from the other layers of fabrics. Similar situations can beobtained regarding the film, inlay and core. Film, inlay and/or core ofa single device may be different in construction.

By ‘different in construction’ is meant that the layers of interest canbe produced by different materials or partly by different materials orthe process of manufacture is different thus giving the layers differentproperties.

The constitutions of a product mentioned above may be surface coated byplasma polymerisation.

The polymeric material as described herein can also be used to coverprostheses of other materials, such as standard prostheses.

In another aspect of the invention the medical device comprises one ormore layers of fabrics which may be surface coated by plasmapolymerisation.

Features of the Product

The thickness of the polymeric product is determined by the number ofpolymer layers and the dimension of these layers in accordance to therequirements of the medical device. The total thickness of the polymericproduct is preferably between 0.001 and 40 cm thick, such as between0.005 and 30 cm, preferable between 0.01 and 20 cm, more preferablebetween 0.02 and 10 cm, further preferable between 0.03 and 8 cm, yetfurther preferable between 0.04 and 5 cm, most preferable between 0.05and 2 cm.

In another embodiment the preferred thickness of a device is about 3 mm.

The surface area of a medical device may be between 1 cm² and 200 cm².

The surface dimension of a medical device comprising the polymericlayered structure as described herein may be between 0.01 to 40 cmaccording to length and width, such as between 0.05 to 35 cm, forexample between 0.09 to 30 cm, preferable between 0.1 to 25 cm, morepreferable between 0.2 to 23 cm, further preferable between 0.3 to 19cm, yet further preferable between 0.4 to 17 cm, most preferable between0.5 to 15 cm. Other preferred sizes of the surface dimension of amedical device may be between 0.5 to 8 cm according to length and width,such as between 0.5 to 7 cm, for example between 0.5 to 6 cm, preferablebetween 0.5 to 5 cm, more preferable between 0.5 to 4 cm, furtherpreferable between 0.5 to 3 cm, yet further preferable between 0.5 to 2cm, most preferable between 0.5 to 1 cm.

The surface dimension according to length and width of layers of fabricin a medical device as described herein may be substantially equal,equal or different from the surface dimension of the medical device.Preferred is a size where any surplus of fabric is removed followingmanufacture of the medical device.

To enclose one or more inlays with fabrics, the size of fabric accordingto the surface dimensions length and width may be the same as for theinlay, substantially the same as for the inlay or somewhat larger thanthe inlay. One or more inlays may be enclosed by two or more layers offabric. Said layers of fabric may have surface dimensions adjusted tocover all the inlays, although the inlays may have distance between eachother. Two or more inlays of a device may or may not be positioned inbetween the same two layers of fabric.

The surface dimension according to length and width of layers of film ina medical device as described herein may be substantially equal, equalor different from the surface dimension of the medical device. Preferredis a size where any surplus of fabric is removed followed manufacture ofthe medical device.

The surface dimension according to length and width of layers of core ina medical device as described herein may be substantially equal, equalor different from the surface dimension of the medical device. Preferredis a size substantially equal to the surface dimension of the medicaldevice.

The surface dimension according to length and width of layers of inlayin a medical device as described herein may be substantially equal,equal or different from the surface dimension of the medical device.Preferred is a size where the inlay is smaller than the surfacedimension of the manufactured medical device.

To increase the strength of the polymeric product, the layers of fabricmay be turned according to each other, hereby the fibres of thedifferent layers of fabric is positioned into different directions. Thefabric may be turned between about 0 to about 90 degree, such as between10 and 80 degree, preferred is between 20 and 70 degree, more preferredis between 30 and 60 degree, further preferred is between 38 and 52degree, yet further preferred is between 42 and 48 degree, mostpreferred is about 45 degree in relation to the former and/or next layerof fabric.

Method for Preparation

Polymers may be prepared by methods known to the person skilled in theart. Chemical catalysis, thermal induction or photo induction areanecdotal non-limiting examples of methods of preparing the polymers.

The polymeric product is prepared according to the descriptions above byconnecting the stacked polymer layers by heating. The heatingtemperature is selected below the melting temperature of the fibrecrystallites in order not to loose the crystallinity of the polyethylenefibres and to a level where the fibres of the fabrics are not melted,destroyed or damaged, ie. below 250 degree Celsius, and above themelting temperature of the polyethylene plastomer, ie. in the rangebetween 80 and 250 degree Celsius, such as between 90 and 240 degreeCelsius, preferable between 100 and 230 degree Celsius, more preferablebetween 110 and 220 degree Celsius, further preferable between 120 and210 degree Celsius, yet further preferable between 130 and 200 degreeCelsius, most preferable between 140 and 190 degree Celsius.

In an embodiment the heating temperature is preferably between 90 and200 degree Celsius, such as between 95 and 195 degree Celsius,preferable between 100 and 190 degree Celsius, more preferable between105 and 185 degree Celsius, further preferable between 110 and 180degree Celsius, yet further preferable between 115 and 175 degreeCelsius, most preferable between 120 and 170 degree Celsius.

In a further embodiment the heating temperature is preferably between 90and 180 degree Celsius, such as between 95 and 170 degree Celsius,preferable between 100 and 160 degree Celsius, more preferable between105 and 155 degree Celsius, further preferable between 110 and 150degree Celsius, yet further preferable between 115 and 145 degreeCelsius, most preferable between 120 and 140 degree Celsius

When heated the short chain polymers of the core or the film or theinlay penetrate into the fibres or filaments or strands of the fabrics,and hereby mechanically connect or bond the polymer layers to eachother. In a preferred embodiment the temperature is selected to a levelwhere the main part of the fabrics is not melted, but a thin layerconstituting a low number of polymer chains or fibres of the outer partof the outermost fabrics of the polymeric product is melted. The heatingprocess may be provided in vacuum and under pressure.

In a further preferred embodiment the temperature is selected to a levelwhere the performances of the reinforcement fibres are not damaged.

The polymer product comprising stratified polymer layers as describedabove, which has been subjected to the heating process, may be stored atroom temperature until use. The polymeric product is preferable capableof being stored for long periods of time, such as several years. Storingis performed in dry conditions at room temperature and in darkness or atleast without direct sunshine to the product. Dry conditions may behumidity of about 10-90%.

Shaping the Medical Device

In the heating process described previously or following a storageperiod of the fused polymer layers, the polymeric product comprising thepolymer layers may be subjected to vacuum and may simultaneously bepushed or pressed into a mould to form the polymeric product. The vacuumprocess prevents the formation of bubbles and protects the polymer fromoxidative degradation. Shaping can also be performed without vacuum butdue to pressure optionally combined with heating the polymeric product.

The vacuum of the method described above may be below 500 mbar,preferable below 300 mbar, more preferable below 100 mbar, furtherpreferable below 50 mbar, yet further preferable below 10 mbar, mostpreferable below 1 mbar.

To secure the desired shape of a device, the pressure of the device inthe shaping process may be maintained until the polymer product iscooled preferable to room temperature. This cooling under pressuresecures consolidation of the product.

The pressure in the process described above is a pressure high enough topress the product into a mould, the pressure may be a low pressureperformed for a long period or a high pressure performed for a shortperiod, or a pressure in between. Low pressure in this context is thepressure just enough to press the product into a mould.

The shape of the pressed polymer product may be any possible figure ineach dimension where the shape may constitute a surface being flat,curved, waved, undulated, bent, bowed, crooked, while the overall shapeof the device may be but is not limited to circular, oval, triangle,squared, rectangle, cubed, bowl, cup, crown, cap, basin, heart, egg,kidney, figure of eight, preferred shape is cup or hemispherical. Thethickness of the device may also vary.

The polymer product pressed into a shape as described above, may bestored at room temperature for long periods of time, such as severalyears. In an embodiment the polymeric product may be produced with oneor more apertures, holes, gaps, perforations or hollows. Said aperturesetc. may constitute an improved attachment and/or optimise the functionof the device. The improved attachment may be obtained without furtherprocessing as the apertures may constitute a shape of the device in away that the device better fits into the location of the body. Theapertures can also be utilised to fasten the device within the body.

Fastening methods are known to persons skilled in the art, and arehereby incorporated.

The apertures etc. may be created simultaneously with the shaping of thepolymeric product, hereby the mould has points, tips or peaks, whichcreate the apertures in the polymeric product. Another method ofproducing apertures etc. is to make a hole by a drill or another boring,cutting or pressing apparatus. Followed the formation of apertures etc.by drilling, cutting or pressing holes, the edge of the apertures on thepolymeric device may be closed.

To the polymeric material may be attached a component, said componentbeing polymeric or non-polymeric. The attachment may constitute part ofa prosthesis or provide an anchorage point.

Collar

Following the shaping of the polymeric product as described elsewhereherein, surplus of polymeric material can be removed e.g. by cuttingoff. Cutting off the surplus of polymeric material leaves a polymericproduct with right angle edges. These edges have to be rounded to secureno damage of the product is performed within the animal or human bodywhen function as a medical device within said body.

In an embodiment the rim of the device may be treated to fix loose endsof fibre or strands. The rim may be closed by sewing or by fastening apolymer ring or a metal ring. When using a ring to close the rim of thedevice, said ring may be 0.55-5 mm thick, preferred is 3 mm.

In another embodiment a collar is placed on the medical device whensurplus of material is removed. The collar can be moulded directly onthe device e.g. by injection moulding.

The collar as described above can be of any material mentioned in thedescription of the first, second or third polymeric component. Thecollar material of the medical device can be the same material or adifferent material as actually used for the first, second or thirdpolymeric component. Preferred is when the collar is of UHWMPE or LDPE.More preferred is collar of LDPE. Most preferred is when the collar isproduced of the same polymeric component as actually used for the coreor film, due to compatibility between the materials. Within the processthe polymeric component of the collar may melt together with thepolymeric component of the film and/or core.

In an embodiment a cup shaped medical device where the hat brim ofsurplus of material is removed a collar of LDPE is moulded directly onthe cut edges by injection moulding.

Markers

In an embodiment markers are placed within the medical device. Themarkers can be used to visualise, trace or in other ways show theposition of the medical device when inserted into a body. Visualisationcan be performed by methods known to a person skilled in the art, whichis hereby incorporated. One method is X-ray identification. The materialof the markers can be any material, which can be placed within thepolymeric material and can be detected from outside of the body.

In one embodiment the markers are contrast balls. Before closing the rimwith a method described elsewhere, contrast balls are placed within thedevice. The contrast balls which can be any suitable colour such as butnot limited to blue, red or green, can be placed in small holes drilledin the device. The drilled holes can be made at a right angle to thesurface established when surplus of material is removed. Fastening aring to the device or moulding a collar as mentioned above closes theholes. The number of contrast balls are optional, in a cup device 3-10contrast balls may be utilised, 7 contrast balls is preferred.

In another embodiment the markers are made of metal. The shape of themarkers is optional. Preferred are balls of metal. More preferred aremarkers of stainless steel or tantalum. Most preferred are balls ofstainless steel or tantalum. The markers are placed within holes of themedical device drilled from the cut edge appearing when surplus ofmaterial is removed. The number of markers is optional. The number ofmarkers is preferably 1-10, such as 2, e.g. 3, such as 4, e.g. 5, suchas 6, e.g. 7, such as 8, e.g. 9, such as 10. The placing of the markersmay be optional. Preferably the markers are placed asymmetrically aroundthe cut edge of the medical device. This asymmetric placement ensuresthe possibility to measure if the medical device changes position whenimplanted in the body. In a cup-shaped medical device the asymmetricplacement of the markers is preferable an asymmetric placement accordingto the circle comprising the cut edge of the medical device, hereby itcan be visualised within the body whether the cup rotates. The cut edgeis closed with a method described elsewhere herein.

In a further embodiment the markers are small pieces of the markingmaterial. The small pieces are placed within the core or inlay whenthese are moulded.

In another embodiment the markers are formed as threads, and are placedwithin the core, inlay, film or fabric when these are produced. Threadsof markers can also be placed between the fabric and any of the core,inlay or film when the medical device is constructed from saidcomponents.

Finishing Treatment of a Medical Device

The present invention in particular relates to material formulationsintended to meet the specifications of durability, bio-compatibility,and strength. These properties are obtainable by treating polymermaterials, such as polyethylene, polypropylene or polyvinylpyrrolidoneor combinations and co-polymers thereof as well as precursor materialsfor polymerisation, with high-energy electrons, gamma rays, photons,microwaves, ion implantation, plasma treatment, annealing, thermalradiation or another radiation to obtain ideal durability andbio-compatibility of the new, modified material. Treatment of theabove-mentioned materials with radiation leads to cross-linking ofpolymers and thereby generating new, modified materials. Preferably, thepolymer material is a cross-linked polyethylene or polypropylenematerial. More preferably the polymer material is a cross-linkedpolyethylene material.

The properties of the materials to be obtained by the cross-linkingprocess are preferably resistant to tear and wear; and have goodcompressibility.

The medical devicemay be packed in a pouch, which is suitable forirradiation. Preferred are pouches of aluminium, more preferred arelaminated pouches of PE, aluminium and PET, where PE (polyethylene)comprises the inner of the pouches and PET (polyethylene-terephthalat)comprises the outer of the pouches.

A pouch with a medical devicemay be filled with nitrogen before it ismade airtight. The medical devices are then subjected to irradiation tocross-link the polymeric material and sterilise the medical device.

In order to increase stability of the medical polymeric device thepolymers of the shaped polymer product may be subjected to furthertreatment, such as cross linking. In a preferred embodiment the crosslinking treatment is conducted in order to cross link only a fraction ofcross linkable polymers in the product. Accordingly, the products may becross-linked by radiation, the cross-linking of the polymers may also bedone by other methods known to the person skilled in the art. Saidradiation may be but is not limited to high-energy electrons, gammarays, photons, and microwaves. Cross binding the polymers improve thestrength of the product. A preferred radiation process is cross-linkingof fibres using treatment with accelerated electrons. As thecross-linking process takes place in the amorphous polyethylene regions,the optimal dose will depend on the fraction of amorphous polyethylenein the final device. The optimal radiation dose is preferably close tothe gelation dose of polyethylene and thus lie between 10^(−10,000) kGy(0.1 and 100 Mrad), preferred is between 10 and 300 kGy, most preferredis 200 kGy.

The radiation can be performed in one uninterrupted treatment, where thecomplete dose of radiation is given to the material. The radiationprocess may also be performed in pulsing or interrupting treatments,where the total dose of radiation is given in 2-15 shorter with aninterval of 1 to 60 minute. Preferred is 25 kGy given eight times with10 min interruption between each radiation treatment (total 200 kGy).More preferred are two times 25 kGy interrupted by 1 to 60 minutes andrepeated 4 times with 10 hours to 1 day of interruption.

The radiation may be performed for the entire product or device or onlypart of the product or device is radiated by using a shield or screenbetween the irradiation source.

When using radiation, the radiation process described may be followed byannealing. The purpose of annealing is to eliminate long living freeradicals by a heat treatment of 80° C. for about 1-12 hours in vacuum.More preferred is 70-85° C. for about 16-24 hours in an inertatmosphere. Preferred is when the inert atmosphere is Nitrogen.

Typically, a device is prepared by a process comprising the followingsteps:

-   -   The device is formed under vacuum by pressing the laminated        polymers in a mould of specified dimensions. The polymer is        chosen from the above mentioned polymers.    -   After hardening the material as formed, or after swelling in a        suitable solvent, the device may be subjected to high-energy        electrons, gamma rays or another radiation in order to create        cross-linking which will modify the mechanical properties of the        material to meet the preferred specifications.    -   Finally, after removal of the swelling solvent, the surface of        the material may be treated to achieve good surface properties        as described elsewhere.

The medical devices may be subjected to annealing when they areirradiated. Annealing is performed in an oven at about 80° C. for a fewhours to remove residual free radicals. Or annealing is performed asdescribed elsewhere herein.

Surface Coating

The surface of the device can subsequently be treated to modify surfaceproperties such as wetting ability and/or biocompatibility. This surfacetreatment can be performed by plasma treatment, chemical grafting or bya combination of plasma polymerisation and chemical grafting. Thematerial contacting with the biological surfaces may be smooth,biocompatible, preferably self-lubricating, and it should bewear-resistant so that particles generated due to wear are avoided inthat this could otherwise result in foreign body reactions and causefurther trouble to the function of the part of organism where themedical device is located.

Furthermore, the surface material should preferably be a material or acombination of materials having self-repairing properties so thatfissures, cracks or other ruptures on the surface do not exceeduncontrollable levels. However, the surface material is preferablycontinuous with the material of the rest of the device, e.g. thematerial may gradually merge into the material of the fabric, film orcore of the device. In this context continuous means that the surfacematerial cannot be pulled away from the material beneath.

The surface of the material may be chemically treated so as to soften,rigidify or lubricate the surface of the device or parts thereof. Thesurface of the material may be coated so that the coating confers theseproperties, or may be treated so as to chemically alter the surface ofthe device so as to confer any of these properties. Alternatively,certain polymer surfaces may be modified by means of thermal orphotolytic energy.

Without being bound by theory it is also believed that a wetted surfacereduces the risk of having the immune system recognising the device whenimplanted, which would otherwise lead to adverse effects of the device.

In one embodiment the surface of the devicemay be coated by a plasmapolymerisation, using low-power plasma equipment. The monomers used forthe plasma polymerisation are any monomer forming a hydrophilic polymerby plasma polymerisation. Preferred are monomers formingpolyvinylpyrrolidone and poly-ethylene-glycol like polymers, mostpreferred is 1-vinyl-2-pyrrolidinone.

The surface coating performed as described above has a thickness of 1 to700 nm, such as between 10 and 500 nm, preferable between 20 and 400 nm,more preferable between 30 and 300 nm, further preferable between 40 and200 nm, yet further preferable between 50 and 100 nm, most preferablebetween 60 and 90 nm.

In another embodiment the surface coating performed as described abovehas a thickness of 1 nm to 5,000 nm, such as between 5 and 2,500 nm,preferable between 10 and 1000 nm, more preferable between 30 and 500nm, further preferable between 40 and 400 nm, yet further preferablebetween 45 and 300 nm, most preferable between 50 and 250 nm.

Plasma is ionised gas. In an artificial plasma to be used for plasmatreatment and plasma polymerisation, the concentration of ionisedspecies is preferably 0.1-10 ppm. Two phases exists in artificialplasma: A gas-phase comprising an energi corresponding to thesurrounding temperature, usually room temperature. In a plasma-phaseions and electrons have an energi at approximately 2-10 eV.

The artificial plasma may be established by exposing a gas with electricfield. The pressure of the gas is preferably 0.01-1 mbar. The electricvoltage utilised is dependent of different features such as thepressure, the composition of the gas, electrode configuration, the sizeof the polymerisation chamber, and frequencies of the electricity. Thevoltage is typically 200-10,000V.

In a preferred embodiment of the plasma polymerisation1-vinyl-2-pyrrolidinone (VP)may be polymerised to polyvinylpyrrolidone(PVP) in a plasma with low energi. The plasma functions as an initiatorfor the polymerisation by formation of radicals in the surface of theelement to be coated. From the radicals the polymerisation process takesplace where monomers of VP polymerise to PVP. A low energy is necessarynot to destroy the monomer VP in the gas-phase as well as thepolymerised PVP. In a preferred embodiment the energy is 0.1-1 W/IL.

In the plasma polymerisation treatment a carrier gas is used, preferredis an inert gas, such as argon or helium.

The chamber for performing the plasma treatment is constructed toperform a homogeneous surface coating of the device by the plasmapolymerisation process.

The surface coated polymeric product is preferably sterilised byradiation or by heating. The radiation can be but is not limited tohigh-energy electrons, gamma rays, photons, microwaves.

The polymeric product may by cross-linked and sterilised simultaneouslyby treating with ionizing radiation or by heating. Preferred iscross-linking by radiation.

Mechanical Properties

The structure of the material of a device may comprise a layered orlaminated structure, a core of one material or one or more interposedlayers with different properties enabling an overall function of thedevise suitable for providing a spacer function and/or to exert pressuredistribution of joints and/or to provide at least part of thesliding/rotating movement of joints by internal movement of the device,or relevant part of the device. However, it is preferred that thematerial itself does not comprise interposed layers resulting in slidingbetween the layers and thereby tear on the mating surfaces within thedevice. Accordingly, the body of the device should be one continuoussolid or semi-solid material.

Mechanical properties for certain relevant polymers are described bySzycher (Szycher, M. (editor), sponsored by SPE, Society of PlasticsEngineers, Inc. Biocompatible Polymers, Metals, and Composites, pp.725-727, 757-61).

Mechanical properties of polymers are controlled by the elasticparameters, the three moduli: elastic, shear, and compressive moduli.These parameters are theoretically interrelated. A modulus is the ratiobetween the applied stress and the corresponding deformation. Thereciprocals of the moduli are called compliances. The three elasticmoduli have the dimension: force per unit area, (N/m² or Pa). Polymersare not normally ideal elastic bodies, but under load they show (timedependant) viscoelastic properties. By taking the load intoconsideration, the properties should be viewed according to thisdilemma. Also, ideal elastic properties and ultimate properties areinfluenced by the viscoelastic properties.

Ultimate tensile strength is a measure of the stress required to causethe material to rupture in tension. Ultimate elongation is the percentstretch of the material before it ruptures in tension. Elongation (%) ismeasured as$\text{Elongation~~(percent)} = {\frac{S_{B} - S_{o}}{S_{o}} \times 100}$

where S_(B)=observed distance between bench marks of the stretchedspecimen at rupture, and S_(O)=the original distance between benchmarks. TABLE 1 Elastic parameters and their definitions Elementary modeof deformation Elastic parameter Symbol Isotropic (hydrostatic) Bulkmodulus K compression bulk compliance or com- κ pressibility (κ = 1/K)Simple shear Shear modulus or rigidity G Shear compliance J (J = 1/G)Uniaxial extension Tensile modulus or E Young's modulus Tensilecompliance S (S = 1/E) Any Poisson ratio ν Symbol Definition K$\frac{{Hydrostatic}\quad{Pressure}}{\begin{matrix}{{Volume}\quad{change}\quad{per}} \\{{unit}\quad{volume}}\end{matrix}} = {\frac{p}{{\Delta V}\text{/}V_{0}} = \frac{{pV}_{0}}{\Delta V}}$κ (κ = 1/K) reciprocal of foregoing G$\frac{{Shear}\quad{force}\quad{per}\quad{unit}\quad{area}}{\begin{matrix}{{Shear}\quad{per}\quad{unit}\quad{distance}} \\{{between}\quad{shearing}\quad{surfaces}}\end{matrix}} = {\frac{F\text{/}A}{\tan\quad\gamma} = {\frac{\tau}{\tan\quad\gamma} = \frac{\tau}{\gamma}}}$J (J = 1/G) reciprocal of foregoing E $\begin{matrix}{{Force}\quad{per}\quad{unit}} \\\frac{{cross}\text{-}{sectional}\quad{area}}{{Strain}\quad{per}\quad{length}}\end{matrix} = {\frac{F\text{/}A}{\ln\quad\left( {L\text{/}L_{0}} \right)} = {\frac{\sigma}{ɛ} = \frac{F\text{/}A}{{\Delta L}\text{/}L_{0}}}}$S (S = 1/E) reciprocal of foregoing (strain/stress) ν $\begin{matrix}{{Change}\quad{in}\quad{width}} \\\frac{{per}\quad{unit}\quad{width}}{\begin{matrix}{{Change}\quad{in}\quad{length}} \\{{per}\quad{unit}\quad{length}}\end{matrix}}\end{matrix} = \frac{{lateral}\quad{contraction}}{{axis}\quad{strain}}$

Examples of ranges of the mechanical properties of the device arementioned below. However, it should be contemplated that not all of thefollowing characteristics may be fulfilled by the material of theprosthetic device since, as explained above, the numerous properties ofthe material are theoretically interrelated. Accordingly, conflict infulfilling all parameters within the stated ranges may occur.

In one embodiment, the prosthetic device according to the invention is adevice wherein the material of the device or at least the part of thedevice which exerts the pressure distribution and/or the part whichexerts the sliding/rotating movement in the joint when the joint isloaded has/have one or more of the following propeties (under biologicalconditions (37° C., physiological salinity)): A compressive modulus (K)of at least 2000 MPa, a shear modulus (G) of at least 1 MPa and anelastic module (E) of at least 10 MPa.

Furthermore, certain requirements to the material under stress withforces that ultimately leads to disintegration can be expressed. Basedon the elasticity parameters for the material, the properties of thematerial with respect to pressure, elongation, torsion and displacementin the range where the material responds elastic can be estimated. Theultimate limits should preferably be within ±20% of the range of elasticresponse. As a consequence thereof, the limits for the ultimateproperties (ultimate compression strength, tensile strength, torsionalstrength, shearing strength) can be derived. Furthermore, the materialshould have an “ultimate percentage elongation” of at least 20%.

The materials according to the invention may be a “quasi elastic”material. Y. Shikinami and H. Kawarada, Biomaterials 19, 1998, pp.617-635, discuss that many materials of biological origin, has a J-formin a stress vs. strain curve, whereas may synthetic materials has anS-form.

Preferably, the critical surface tension (γ_(c)) values should be withinthe “zone of bio-compatibility” corresponding to the range of about20-30 dynes/cm (as defined by Lelah M. D., Cooper, S. L., Polyurethanesin Medicine-CRC Press, Inc. Boca Raton, Fla., pp. 59-42 and 92-93).

Additives

A device constructed from the polymeric product may comprisebiologically active additives. Medication or biological activesubstances can be used as additive to the device to facilitate healing,minimise destruction or with other therapeutic goals, such as painrelief, anti-inflammation, oncology treatments, stimulation of bonegrowth, and/or anti-infectious agents. Also, biological osteogenic orchondrogenic, chondral inductive, and/or chondral conductive materialsmay be added to the device. In particular patents suffering fromosteoporosis or other bone degenerating conditions may benefit fromhaving devices comprising osteogenic inductive materials implanted.

The medication or biological active substances can be used as additiveto the device to facilitate cell growth, such as osteocytes;osteoblasts, chondrocytes, chondroblasts, mesenchymal cells. Cartilageinducing factor may for example be the factors described in U.S. Pat.No. 4,774,322 and U.S. Pat. No. 4,843,063.

In another preferred embodiment, additives such as lubricants, dyes,stabilizers and other process enhancing compounds are incorporated intothe polymeric mixture. Such compounds may not necessarily enhance thestrength or structural integrity of the final polymeric matrix, but doaid in the manufacturing process or enhance the overall appearance ofthe finished article. Examples of these compounds may be long chainfatty acids and their salts, organic and inorganic coloring agents, freeradical inhibitors, pH buffering agents and other materials known toenhance processing of polymers within the polymer industry.

In another preferred embodiment of the present invention, solidmaterials may be incorporated into the polymer or resin mixtures. Suchsolid materials may be, for example, chopped carbon or glass fiber ornanotubes, carbon black, graphite powder, talc, mica, polyamide fiberand other fillers commonly used in the polymer industry. As is known inthe polymer industry, such fillers may be advantageously added to apolymer matrix for the purposes of enhancing strength, durability, bulkdensity, machineablity of the resulting polymeric article. Of, coursethe above list is not exhaustive and other uses of the fillers may alsobe contemplated.

Devices

One preferred device produced of the polymeric product described hereinmay be a substitution for cartilage. Said cartilage substitution mayreplace damaged cartilage between intact bones, or it may be part of amedical prosthesis comprising cartilage substitution.

A device produced of the polymeric product itself can be used as agrowth medium and/or network for the natural or artificial cells, suchas chondrocytes.

A device made from the polymeric product described above is capable ofbeing formed to suit into parts of the organism as described elsewhereherein. Especially the device is suitable to be used in animals, such asmammals and human beings, preferred is human beings. The animals, towhich the medical device may be utilised, may be selected from the groupof mammals, such as but not limited to horses, dogs, cats, cows andmonkeys.

In one embodiment the device is especially constructed to be utilised tosupport, hold, sustain, bear, carry, replace or displace anyconstitution within the mammalian body, which comprises high shapestability and good wear resistance.

The polymeric product is adapted not to interfere with intra-articularor other components when the device is in the body of a human.

The polymeric product as medical device may be but is not limited to beused as joint spacer implant in joints of knees, hip, shoulders,fingers, wrist, elbow, spine, neck, loin, toes and ankles. Especiallythe devices are used in diseased patients with osteoarthriticdegeneration of joints. The implants with a smooth articulating surfaceoppose the diseased and degenerated cartilage joint facet, which isexpected to lead to reduced force and stresses and improved mobility inthe joint with consequent reduced pain and improved functional capacityof that joint.

The medical device as described herein may be produced in a number ofsizes corresponding to the natural variety of the bones within the jointwhere it is intended to be used as well as to the differences in bonesize due to the age or size of individuals.

Moreover, non-interference of the intra-articular components may beachieved by a hole which runs through the body of the device; that is tosay the device may comprise a hole through which intra-articularcomponents may pass. When loading the device, the slits may serve topass intra-articular components through the body of the device. Theslits in this embodiment run from the periphery of the body of thedevice to the hole through which the intra-articular components passafter the device is implanted or loaded.

Typically, and to at least some extent, the device is adapted in itsstructure and/or material composition to alleviate conditions associatedwith worn cartilage by providing a spacer function and/or to exertpressure distribution in the joint when the joint is loaded and/or toprovide at least part of the sliding/rotating movement of the joint byinternal movement of at least part of the device.

It is also an object of the present invention to provide a method fornon-invasive locking of a device within a joint. In addition, the methodis independent of use of cement or bony ingrowth of the device.

The device may completely or substantially completely surround anintra-articular component or other components of the organism.

A device made from the polymeric product described above is capable ofbeing formed to suit any joint cavity of animals or human beings,therefore the device may for example be formed to fit into any one ofthe following joints: Hip joint, knee joint, ankle joints, shoulderjoint, elbow joints, wrist, fingers, spinal column joints, such as forsubstituting intervertebral discs, and the jaw joint.

The medical device may constitute the surface of a prosthetic device. Itmay be the entire surface or part of the surface of a prosthetic deviceAlso the device may constitute a complete or part of a hipendo-prosthesis, or it may be a breast prosthesis, a stent, a catheter,a heart valve or cartilage substitution.

Generally, the invention comprises the polymeric product as describedabove from which different medical devices may be manufactured, also themethod of producing said polymeric product and medical devices isenclosed within the invention. Enclosed are methods of producing apolymeric product and medical devices as described above, as well as anycombination of the features described for said polymeric product andsaid medical devices.

Another aspect of the invention is a method for producing a polymericproduct, said method comprising obtaining a number of at least threepolymer layers, and positioning the polymer layers in a sandwichcomposition, forming the sandwich composition of polymer layers byheating said composition followed by pressing it into a mould, where theheating and pressing processes are conducted in vacuum, and providingthe polymeric product in a desired shape.

In the method for producing a polymeric product wherein the polymericproduct is as described above, at least three polymer layers isutilised, these polymer layers constitute a core with at least one layerof fabric on each side, where the core differs in constitution from thefabrics, preferred is the method for producing a polymeric product wherethe fabrics at the different sides of the core have equal constitutions.

The method for producing a polymeric product comprise two or more layersof fabrics, where said two or more layers of fabrics have a film of apolymer layer in between each fabric.

In the method for producing a polymeric product the core and the filmhave similar composition except for the thickness of the polymer layer.The thickness of the polymer layers is as described above, in apreferred embodiment the film is between 0.01 and 2 mm thick, and thecore is between 0.1 and 10 mm thick. In an embodiment the method forproducing a polymeric product comprises fabric, film and core where thestructure of the fabric are composed of long polymer fibre, and the coreand film are composed of short chain polymers. These polymer fibres canbe selected among polyethylene (PE), polypropylene (PP) andpolyvinylpyrrolidone (PVP). Most preferable is polyethylene (PE). Thelong polymer fibres are ultra high molecule weight polyethylene (UHMWPE)fibre and the short chain polymers may branched.

In an embodiment the method for producing a polymeric product comprisesfabric which is manufactured, e.g., woven, into a shape or form suitablefor the shape of the polymeric product. Said fabric consist of UHMWPEfibres in which the intersects are positioned as formerly described,preferably in angles of about 90 degree.

In an embodiment the method for producing a polymeric product comprisesfabric which has high tensile strength and high wear resistance, and acore which absorbs shocks, pushes and strokes.

The method for producing a polymeric product comprises arranging thepolymer layers in the order of fabric, film and core in accordance tothe description above. The most preferred constitutions are listedabove. The polymer layers are heated, and under vacuum the polymericproduct is pressed in to a mould. The device, which is formed, istreated by ionising radiation, to further cross bind the polymers andthereby improve the strength of the product. The product is furthersubjected to annealing to ensure all linking has appeared.

In an embodiment the method for producing a polymeric product comprisessurface coating of the annealed polymeric product and further thepolymeric product is sterilised by ionising radiation or by heating.

In another embodiment the method for producing a polymeric productcomprises annealing the polymeric product before it is subjected tosurface coating.

In a further embodiment the method for producing a polymeric productcomprises simultaneously cross-linking and sterilisation of thepolymeric product by treating with ionising radiation or by heating.

In an embodiment the method for producing a polymeric product comprisessurface coating of the polymeric product, as formerly described.

In a preferred embodiment the method for producing a polymeric productcomprises production of the polymeric product where the shape and sizeof the polymeric product can be any possible to produce by pressing intoto a mould, said mould forming a polymeric product which can be flat orround or in between and where the three-dimensional shape can be anypossible forming by pressing into a mould.

The polymeric product can be utilised to produce a prosthetic devicecomprising polymer layers, the order of the polymer layers, and themethod of production of the polymeric product as described above.

Preferred is a method of producing a prosthetic device of three polymerlayers, which constitute a core with at least one layer of fabric oneach side. Another preferred constitution is a core which at each sidehas two layers of fabric with a film in between. A further preferredconstitution is a film between two layers of fabric.

In a preferable embodiment of the method the prosthetic device areproduced from polymer layers composed of a polymer selected amongpolyethylene (PE), polypropylene (PP) and polyvinylpyrrolidone (PVP).Most preferable is a prosthetic device wherein the polymer layers arecomposed of polyethylene (PE).

In a further preferable embodiment of the method the prosthetic deviceare composed of fabrics of long polymer fibre, which preferable areultra high molecule weight polyethylene (UHMWPE) fibre or otherpolyethylene fibre as previously described, whereas the core and thefilm are composed of short chain polymers, the short chain polymers maybe branched.

The fabric is of medical grade and is woven into a shape suitable forthe shape of the polymeric product. The shaping and physicalcharacteristics is determined by the arrangement of the UHMWPE fibres,said fibres can have intersects in angles αs described formerly.

In a preferred embodiment the prosthetic device has a high tensilestrength and a high wear resistance due to the properties of thefabrics, whereas the core absorbs shocks, pushes and strokes.

The polymeric constitution of the prosthetic device is obtained inaccordance with the details given above where the polymer layers areheated, subjected to vacuum and pressed into shape in a mould, andfurther treated as described above.

EXAMPLES Example 1

Artificial Cartilage Cup

The artificial cartilage cup is an artificial joint spacer made toreplace the missing or damaged cartilage so the joint can stay mobile.

The cup is based on a sandwich construction with a LDPE core reinforcedon both sides with UHMWPE fiber fabric.

At the edge metal markers makes it possible to trace the cup whenimplanted.

The round LDPE collar of the cup makes a cup without sharp edges andcaptures the metal markers.

Finally a crosslinking of the polymer improves the performance of theLDPE core.

The production process includes the following steps:

Injection Moulding of Base LDPE Disk

The LDPE disk is made of pellets/granulates in the injection mouldingprocess. The disk is approximately five mm. thick and 134 mm indiameter. One standard disk size will later be formed to different sizeof cups.

Pressure Consolidation with UHMWPE Fiber Fabric

Two pieces of 20×20 cm UHMWPE fiber fabric are placed on each side ofthe disk and the sandwich are pressed to form a cup with a surplusmaterial like an irregular hat brim.

Different cup sizes are produced and identified by an individual number.

Shaping the Cup by Cutting off Excess Material

Cutting off the hat brim leaves a cup with right angle edges.

Drilling of Cup Holes and Mounting of Metal Markers

Metal markers in the cup make tracing the cup in the body possible. Forthe first test production, the markers are tantalum balls, and for laterproduction, the markers will be stainless steel balls.

Injection Moulding of LDPE-Collar on Cup

The metal markers are fixed, and LDPE-collar covers the right angleedges.

Packaging with Nitrogen Gas

In a packing machine, the cup is packed in an aluminum pouch withnitrogen gas, and the pouch is sealed to prevent oxygen from being incontact with the cup. Oxygen will hinder the later crosslinking process,as it reacts with the free radicals. The aluminium pouch is put in ashipment box, ready for sending to the crosslinking plant.

Crosslinking and Sterilization

The cup goes to the irradiation plant, is irradiated and returns to theproduction area. The irradiation forms free radicals. The free radicalsare very reactive places in the polymer material, which react to formcrosslinking in the polymer. The irradiation dose is about 200 kGy.

Annealing

Just after the irradiation process, there are still free radicals. Inthe annealing process, the free radicals form crosslinking. Theannealing process is a heating at approximately 75° C., which speeds upthe crosslinking reaction without softening the cup. The process isslowly running even at room temperature, but might take about one month.The temperature must be at a relatively low level in order to avoidsoftening and deforming of the cup.

Final Packing, Releasing and Storing

The cup is packed in inner box, labelled and instructions for use aresupplied. The product is released after a quality check, and stored atthe subcontractor.

Example 2

The cup-shaped medical device constructed as a three layered devicecomprising fabric-film-fabric was tested to assess wear properties usinga machine intended to simulate the tribological conditions encounteredin the human hip joint.

In this example a test machine ‘8800 Instron System’ has been used.

Results: Following simulation where the device has been treated by1,000,000 movements of a 100 Kg person, no debris of the material hasbeen observed.

The simulation was continued to 15,000,000 cycles with a load patternsimulating walking. The load varied between 2500 N and about 150 N andthe cup rotated in a rotation angle between +15 and −15 degree. The testwas regularly stopped with intervals around 1 million cycles, and thespecimen was taken out for inspection and photographing.

From 5 to 15 million cycles the thickness of the specimen was measuredat each inspection. The wear rate is approximately 3040 μm per 1 millioncycles.

Example 3

Knee Joint

The artificial polymer composite intraarticular implant with improvedsurface friction modalities should be bipolar with femoral componentcovering the cartilage area of the medial and lateral femoral condyles,and adjustments and alignment according to cruciate ligaments should beperformed.

The thickness is between 2 to 4 mm. The shape mimics the articularsurface of conventional total knee arthroplastes.

The tibial component is constructed in same material as above, and theshape and contour follows the meniscus including the central joint area.The implant is connected with an anterior bridge in front of theattachment of the anterior cruciate ligaments attachment on tibia.

Both components are unconstrained to each other and unconstrained to thefemoral and tibial parts of the human joint.

The fixation or stability of the implant is dependent on macrostructureof the bony parts and the joint capsule. The stiffness of the implantensures no roll up phenomenon of each implant component.

Example 4

Ankle Joint

The artificial polymer ankle joint spacer implant consists of a materialclose to that mentioned in the example of knee joint.

The implant is monopolar and its extension-corresponds to the cartilagearea of the talar bone of the ankle joint. The thickness is between 2 to4 mm.

The rim of the implant possess a softer rim, holds the implant duringloading and flexion and extension.

Example 5

Shoulder Joint

The artificial polymer shoulder spacer implant consist of a materialclose to that mentioned in the example of knee joint.

The implant is monopolar and its extension corresponds to the cartilagearea of the glenoid cavitate of the shoulder joint plus some extensionwhich may be 0.5 to 3 cm, which articulates with the cartilage area ofthe head of humerus. The thickness is between 2 to 4 mm. The implantwill be excavated superiorly according to the tendon of the long bicepsmuscle, and it should respect the rotator cuff, accordingly.

The rim of the implant possess a softer rim, holds the implant duringloading and flexion and extension, abduction, inner and outer rotation.

1-101. (canceled)
 102. A medical device comprising a biocompatiblepolymeric product with a layered structure comprising: at least oneupper layer of a first polymeric component, a middle layer at a secondpolymeric component, and at least one lower layer of a third polymericcomponent, wherein the chain length of the first polymeric component andthe third polymeric component is longer than the chain length of thesecond polymeric component.
 103. The medical device according to claim102, wherein at least one of the first polymeric component, the secondpolymeric component and the third polymeric component each isindependently selected from: the group consisting of polyacrylates,polystyrene, polyethers, polytetrafluoroethylene, polyvinylalcohol,polyethylene, polypropylene, polyethylene oxides andpolyvinylpyrrolidone.
 104. The medical device according to claim 102,wherein the first polymeric component and the third polymeric componentare substantially identical.
 105. The medical device according to claim102, wherein the first and third polymeric components are composed oflong polymer fiber, and the second polymeric component is a short chainpolymer material.
 106. The medical device according to claim 102,wherein the first and third polymeric components are ultra high moleculeweight polyethylene (UHMWPE) fiber.
 107. The medical device according toclaim 102, wherein said at least one upper layer of a first polymericcomponent and said at least one lower layer of a third polymericcomponent each comprises a fabric, and wherein the tensile strength of afiber or strand of the fabric is above 1.0 GPa.
 108. The medical deviceaccording to claim 102, wherein the polymers of the second polymericcomponent re short chain polymeric material which may be optionallybranched.
 109. The medical device according to claim 102, wherein themiddle layer is selected from the group consisting of: a core, a film,an inlay and combinations thereof.
 110. The medical device according toclaim 109 wherein the film is between 0.001 and 5 mm thick.
 111. Themedical device according to claim 102, wherein the shape of the deviceis any shape which can be formed by pressing into a mold, and theoverall shape of the device is selected from the group consisting of:circular, oval, squared, rectangle, cubed, bowl, cup, crown, cap, basin,hemispherical, and combinations thereof.
 112. The medical deviceaccording to claim 102, wherein to the polymeric material is attached toa component, said component being polymeric or non-polymeric.
 113. Themedical devices according to claim 102, wherein the device is suppliedwith at least one feature selected from the group consisting ofapertures, holes, gaps, perforations and hollows.
 114. The medicaldevice according to claim 102, wherein the polymeric product is adaptedto be used as a medical device for the body of a mammal.
 115. Themedical device according to claim 102, wherein the polymeric product isadapted not to interfere with intra-articular components when the deviceis in the body of a human.
 116. The medical device according to claim102, wherein said device is utilized to support, bear, carry, replace ordisplace any constitution within the human body, which comprises highshape stability and good wear resistance.
 117. The medical deviceaccording to claim 102, wherein the device at least partially surroundsan intra-articular component.
 118. The medical device according to claim102, wherein the device is a hip endoprosthesis.
 119. The medical deviceaccording to claim 102, wherein the polymeric product constitutes thesurface of a prosthetic device.
 120. The medical device according toclaim 102, wherein the device is a cartilage substitute.
 121. Themedical device according to claim 102, wherein the device is a breastprosthesis.
 122. The medical device according to claim 102, wherein thedevice is a stent.
 123. The medical device according to claim 102,wherein the device is a catheter.
 124. The medical device according toclaim 102, wherein the device is a heart valve.
 125. A method forproducing a biocompatible medical device of a polymeric product, saidmethod comprising: providing at least three polymer layers, comprising:at least one upper layer of a first polymeric component, a middle layerof a second polymeric component, and at least one lower layer of a thirdpolymeric component, wherein the chain length of at least one of the atleast one first polymeric component and at least one of the at least onethird polymeric component is longer than the chain length of the secondpolymeric component, and positioning said polymer layers in a sandwichcomposition, and shaping the sandwich composition of polymer layers byheating said composition followed by pressing it into a mold, where theheating and pressing processes are conducted in a vacuum, so as toprovide the polymeric product in a desired shape.
 126. The methodaccording to claim 125, wherein the at least three polymer layersconstitute a member which is a core or a film or an inlay, said memberhaving at least one layer of fabric on each side.
 127. The methodaccording to claim 126, wherein the member differs in constitution fromthe fabrics.
 128. The method according to claim 126, wherein differentlayers of fabrics have equal constitutions.
 129. The method according toclaim 125, wherein the polymer layers are composed of a polymer selectedfrom the group consisting of; polyacrylates, polystyrene, polyethers,polytetrafluorethylene, polyvinylalcohol, polyethylene, polypropylene,polyethylene oxides, polyvinylpyrrolidone, and combinations thereof.130. The method according to claim 125, wherein the polymer layers arecomposed of a polymer selected from the group consisting of:polyethylene (FE), polypropylene (PP), polyvinylpyrrolidone (PVP) andcombinations thereof.
 131. The method according to claim 126, whereinthe structure of the fabrics are composed of long polymer fiber, and themember is composed of short chain polymer material.
 132. The methodaccording to claim 126, wherein the first and third polymeric componentscomprise long polymer fiber which is ultra high molecular weightpolyethylene.
 133. The method according to claim 126, wherein the fabrichas high tensile strength and high wear resistance.
 134. The methodaccording to claim 125, wherein the second polymeric component comprisesshort chain polymer material which is branched.
 135. The methodaccording to claim 126, wherein the member is a film which is between0.001 and 5 mm thick.
 136. The method according to claim 126, whereinthe member is a core which is between 0.1 and 30 mm thick.
 137. Themethod according to claim 125, wherein the heating is at a temperatureof between 80 and 250 degrees Celsius.
 138. The method according toclaim 125, wherein the vacuum is below 800 mbar.
 139. The methodaccording to claim 125, wherein the shaped product is treated byradiation, to further crosslink the polymers and thereby improving thestrength of the product.
 140. The method according to claim 125, whereinthe shaped product is further subjected to annealing.
 141. The methodaccording to claim 140, wherein the annealed polymeric product issubjected to surface coating, where the product is coated bypolyvinylpyrrolidone (PVP) by plasma polymerization. 142, The methodaccording to claim 125, wherein the thickness of the polymeric productis between 0.001 and 40 cm thick.